The invention relates to a storage system comprising a metal structure, such as a rack. Such storage system is used for stocking at different level of the structure various products. In order to gain place, such storage system enables to stock various product at level up to 3 meters, 5 meters, 8 meters, 15 meters, 20 meters, 30 meters, 40 meters or even more from the ground.
When such a storage system is submitted to seismic vibrations, the risk of collapse of said storage system is high, meaning risks of injuries for people, risk of damaging stored products due to their falls and loss of time, as after a severe seismic vibration, the complete structure needs to be replaced for safety purposes. Furthermore, due to the seismic vibration, efforts are exerted in the concrete floor or platform on which the vertical column are fixed, this efforts leading to damages around the fixation points of the vertical columns.
Many systems have already been proposed for building in order to limit the damage caused by earthquake. For example, U.S. Pat. No. 5,148,642 teaches the use of horizontal girders connecting vertical column, said girders being provided with dissipative zones adjacent to their ends attached to vertical columns, so as to form plastic hinge.
The system of U.S. Pat. No. 5,148,642 requires a long time for its erection, as the system is not easily mounted.
The system of U.S. Pat. No. 5,148,642 comprising plastic hinge horizontal girders does not provide a good solution for storage system, as in case such a structure would have been used, after an earthquake, all the stored product would need to be removed from the storage system for replacing at least the majority of the horizontal girders. This means a cost full and time consuming operation.
The invention relates to a storage system which is able to resist to seismic vibration, and which resistance can easily be restored after a seismic vibration without or with a limited need to displace the stored product out of the storage structure. The storage system of the invention enables thus to minimize the displacement/removal of product out of the structure for replacing one or more diagonal members.
The invention relates to a storage system comprising a metal structure comprising a series of vertical columns linked the one to the other by a series of horizontal members acting as support for the products to be stored or for plates on which are placed the products to be stored, and a series of diagonal members directly connected to vertical columns by means of connecting elements pushing each a face of a portion of a diagonal member against a face of a column. In the storage system of the invention,
at least two diagonal members are provided with at least one dissipative zone being capable of undergoing plastic stretching and functioning as means for providing resistance to seismic vibrations, a first diagonal member having a first end attached to a first vertical member and extending between said ends, a second end attached to the second vertical end and a central part provided with at least one dissipative zone, while a second diagonal member has a first and attached to said second vertical member, a second end attached to said first vertical end and a central part provided with at least one dissipative zone and extending between said ends,
a first linking means connects a portion of the first column adjacent to the first end of the first diagonal member to a portion of the second vertical column adjacent to the first end of the second diagonal member, while a second linking means connects a portion of the second vertical column adjacent to the second end of the first diagonal to a portion of the first vertical column adjacent to the second end of the second diagonal,
said ends of the first and second diagonal members are reinforced so that when a dissipative zone of a central part of a diagonal member is submitted to a plastic deformation, the ends of said diagonal member are only submitted to an elastic deformation and are not detached from the vertical columns, and
the linking means are adapted for undergoing elastic deformation when at least one dissipative zone is undergoing a plastic stretching.
The use of linking means undergoing elastic deformation while one or the two diagonal members undergo a plastic stretching is required for the transfer of efforts to the diagonal members during an earthquake.
Advantageously, the diagonal members are provided with at least one dissipative zone undergoing plastic stretching when submitted to a seismic vibration with an effort or force higher than a predetermined effort or force, while the linking means are not provided with dissipative zone undergoing plastic deformation when submitted to a seismic vibration with an effort or force equal to about 1.2 times said predetermined effort or force, preferably to about 1.3 times said predetermined effort or force.
According to an embodiment, two adjacent columns are linked the one to the other by at least four diagonal members provided with at least one dissipative zone and by at least three linking means connecting one end of a diagonal member to an end of another diagonal member. The diagonal members form crosses, the axis of which are not vertical, nor horizontal. Said axis form for example an angle of 15xc2x0 to 75xc2x0, advantageously from 30 to 60xc2x0 with respect to a horizontal plane. When several crosses (formed by independent diagonal members) connect two adjacent vertical columns, one single linking element or profile is often sufficient for transmitting the effort from one cross to the underneath cross.
Preferably, all the diagonal members are provided with at least one dissipative zone. For example, each diagonal member is provided with at least two (or more, such as three, four, etc.) dissipative zones distant from each other. According to a detail of a possible embodiment, the diagonal member is a profile, the central portion of which is provided with successive openings so as to define a substantially continuous dissipative zone extending along the central portion of the diagonal member.
According to an embodiment, each diagonal member is a profile having a first end connected to a first vertical column, a second end connected to a second vertical column, and a longitudinal portion extending between said ends, whereby said ends are flattened and have a total thickness which is greater than the thickness of the longitudinal portion, advantageously each end corresponds to a folded portion of the profile, so that said end is flattened and have a total thickness at least equal to about twice the thickness of the central part of the diagonal member, most preferably at least equal to about three times the thickness of the central part of the diagonal member.
For example, the diagonal member is formed of a metal, the dissipative zone of a diagonal member being formed by removing materials from the central part of the diagonal member at the place of said dissipative zone. For example, the diagonal member has a longitudinal central part with a cross section, whereby the dissipative zone is formed by removing at least 25% (such as from 25% to 50%, preferably about 30%) of the material in the cross section of one or more portions of the central part.
According to an embodiment, the diagonal member has a longitudinal central with a defined length, whereby the dissipative zone extends on a major portion of the central part.
According to possible diagonal member, the diagonal member is:
a longitudinal profile, the ends of which are folded portion of the profile, said portion being folded around at least an axis parallel to the longitudinal direction of the profile; or
the profile has at least two longitudinal elements connected there between along a folding line, whereby said two longitudinal elements define there between an angle from 15xc2x0 to 175xc2x0 in the longitudinal portion extending between the two ends, while at said two ends, said two longitudinal elements are flattened so as to extend adjacent to each other; or
a profile having a first end connected to a first vertical column, a second end connected to a second vertical column, and a central longitudinal portion extending between said ends, whereby the profile has at least two longitudinal elements connected there between by a longitudinal connecting elements, said two longitudinal elements being at least partly distant from each other in the central longitudinal portion, while being adjacent to each other at the ends.
Most preferably, each end of the diagonal member is flat and connected to a column by means of a single connecting element extending between said end and the column. Said single connecting means is for example a bolt working with a nut, a rod working with abutments means (at least one being mobile), screw, etc. By using one single connecting means for connecting one end to a vertical column, the placement and removal of a diagonal member is easy and rapid, such a easy and rapid removal and replacement being important for storage system, so as to be able to replace quickly diagonal members, the dissipative zone thereof having been plastically stretched after an earthquake. Such a rapid replacement is necessary for ensuring that in case of an earthquake, the diagonal members undergoing plastic deformation can be replaced well before another earthquake occurs, so as to reestablish the properties to resist to seismic vibrations. Moreover, when using two or three bolts for attaching one end of a diagonal member to a vertical member, a possible deformation of the end of the diagonal member will render more difficult the replacement of the diagonal member due to possible tension in one or more bolts.
According to an advantageous embodiment, the dissipative zone is a zone of the longitudinal central part which is provided with openings, whereby each opening having a maximum length measured parallel to the longitudinal direction of the central part and a maximum width measured perpendicular to said longitudinal direction, the maximum length being at least equal to the maximum width, such as at least equal to 1,5 times the maximum width for example equal to 2, 3, 4 times the maximum width. Preferably, the maximum length is lower than 5 times the maximum width.
According to preferred embodiment, the diagonal members with dissipative zone are located in the structure at least near the bottom of the structure, i.e. near the ground. According to a specific embodiment, the structure comprises only diagonal members with dissipative zone near the ground, such as up to height of 3 m, preferably up to a height of 2 meters.
The invention relates also to a storage system comprising members with dissipative zone(s), especially a storage system of the invention, in which at least one dissipative zone of the diagonal member is associated with a means for facilitating the detection of a plastic deformation.
Preferably, the means for facilitating the detection of a plastic deformation is selected among the group consisting of marks distant from each other by a predetermined distance, films which can change of appearance when submitted to a plastic deformation, tapes, wires, sliding means, sliding means comprising one element connected to a first portion of the dissipative zone and another element connected to another portion of the dissipative zone, whereby the first sliding element is adapted to slide with respect to the second sliding element, and combinations thereof.
The invention further relates to a process for storing products in a storage system comprising a metal structure comprising a series of vertical column linked the one to the other by a series of horizontal members, and a series of diagonal members directly connected to vertical columns by means of connecting elements pushing each a face of a portion of a diagonal member against a face of a column,
whereby at least two diagonal members are provided with at least one dissipative zone being capable of undergoing plastic stretching and functioning as means for providing resistance to seismic vibrations, a first diagonal member having a first end attached to a first vertical member and extending between said ends, a second end attached to the second vertical end and a central part provided with at least one dissipative zone, while a second diagonal member has a first end attached to said second vertical member, a second end attached to said first vertical end and a central part provided with at least one dissipative zone and extending between said ends,
whereby a first linking means connects the first end of the first diagonal member to the first end of the second diagonal member, while a second linking means connects the second end of the first diagonal to the second end of the second diagonal,
whereby said ends of the first and second diagonal members are reinforced so that when a dissipative zone of a central part of a diagonal member is submitted to a plastic deformation, the ends of said diagonal member are only submitted to an elastic deformation and are not detached from the vertical columns, and
whereby the linking means are adapted for undergoing elastic deformation when at least one dissipative zone is undergoing a plastic stretching,
in which after a seismic vibration, the diagonal members undergoing a plastic deformation are replaced by new diagonal members provided with at least one dissipative zone.
Advantageously, the diagonal members are provided with at least one dissipative zone undergoing plastic stretching when submitted to a seismic vibration with an effort or force higher than a predetermined effort or force, while the horizontal members are not provided with dissipative zone undergoing plastic deformation when submitted to a seismic vibration with an effort or force at least equal to 1.2 times (preferably at least equal to 1.3 times ) said predetermined effort or force. The process of the invention uses preferably a storage system of the invention as disclosed here above.
In the process of the invention, when the storage system is submitted to a seismic vibration with an effort or force greater than a predetermined effort or force, the diagonal members provided with at least one dissipative zone are stretched in said dissipative zone so as to dissipate in said dissipative zones energy of the seismic vibrations, whereby preventing the collapse of the metal structure. After the metal structure being submitted to seismic vibrations causing a plastic stretching of the diagonal members provided with at least one dissipative zone, said diagonal members are replaced by new diagonal members provided with at least one dissipative zone.